Methods for digestion of cellulosic biomass solids in the presence of a phenolic solvent generated in situ from lignin

A method comprising:

• providing cellulosic biomass solids in a digestion medium comprising water and an organic solvent;
• heating the cellulosic biomass solids and the digestion medium in a digestion unit in the presence of molecular hydrogen and a slurry catalyst capable of activating molecular hydrogen, thereby forming an alcoholic component derived from the cellulosic biomass solids and liberating lignin from the cellulosic biomass solids, the lignin forming a phenolics liquid phase that is partitioned from the digestion medium and at least a portion of the slurry catalyst accumulating in the phenolics liquid phase as it forms;
• removing at least a portion of the phenolics liquid phase and the slurry catalyst accumulated therein from the digestion unit;
• converting at least a portion of the phenolics liquid phase into a phenolic solvent;
• and
• returning at least a portion of the phenolic solvent and the slurry catalyst to the digestion unit, the phenolic solvent becoming part of the digestion medium once returned to the digestion unit.